The continued high prevalence of HIV-associated neurocognitive disorders (HAND) remains a significant public health concern that is the focus of the HIV Neurobehavioral Research Center's Resource and Scientific Objectives. The Neurobehavioral (NB) Core is essential to the goals of the HNRC by providing state-of- the-art support to local, national, and international neuroAIDS studies that examine the prevalence, course, pathogenesis and treatment of HAND. In accordance with the HAND diagnostic guidelines, all participants in the HNRC cohort will undergo a comprehensive NB assessment that will include well-validated measures of neurocognitive functioning, psychiatric status, and everyday functioning. The NB Core's specific Resource Objectives are to provide: 1) demographically-adjusted individual, domain, and global summary scores of neurocognitive functioning across domains sensitive to HIV; 2) Global and domain-specific determinations of NB change in individual participants using reliable and validated actuarial methods (e.g., regression-based norms for change); 3) Self-assessment of cognitive and psychiatric symptoms and any reduced independence in daily functioning; 4) Laboratory-based measures of everyday functioning (e.g., medication management); 5) Current and lifetime history of mood and substance use diagnoses; 6) Interdisciplinary case-conference consensus diagnoses of HAND; and 7) Technical assistance, training, certification, consultation, and career development mentoring. The Scientific Objectives of the NB Core are to support studies regarding the role of aging in the development and expression of HAND, the timing and determinants of HAND in acute and early HIV infection, and the effects of antiretroviral and other treatments for HAND. In particular, the NB Core seeks to support innovative studies that will enhance the classification accuracy (e.g., novel web-oriented tests) and clinical utility (e.g., brief, portable assessments) of everyday functioning assessments for diagnosing HAND. We will also continue to spearhead the development of the next generation of normative NB test standards for under-served populations in the U.S. and developing countries, including recently developed methods for detecting clinically meaningful NB change. The NB Core provides a resource for basic and clinical investigators interested in HAND, and is poised to respond quickly and flexibly to emergent scientific questions in neuroAIDS by providing access to valuable data, well-characterized participants, and expertise in the NB aspects of HIV infection.